Is there a way to convert a line layer (shp or PostGIS) data into (x, y , z, cost) i.e. (From_node, To_node, optional_Elevation, Cost/Weight) ?
Some additional information would be useful to find out exactly how your data looks like and what you are trying to get out of it. The following statement might be a start:
I didn't know where you want the elevation to be measured, so I took the z value at the end point for now.
Update Jul 31:
Update Aug 1:
In OGR, a LineString object has similar functions StartPoint() and EndPoint().